Field of the Invention
The present invention relates to an electrostatic capacitance transducer, a probe, and a subject information acquiring device, and more particularly relates to an electrostatic capacitance transducer relating to a technology in which at least one of transmission and reception of acoustic waves, and to a probe and subject information acquiring device including the same.
Description of the Related Art
Capacitive micromachined ultrasonic transducers (CMUT), which are a type of electrostatic capacitance transducer, are being studies as a substitute for piezoelectric elements. CMUTs are manufactured using a microelectromechanical systems (MEMS) process employing a semiconductor processing, as described in “Capacitive micromachined ultrasonic transducers: fabrication technology,” Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 52, no. 12, pp. 2242-2258, December 2005.
A CMUT cell is a configuration where, a vibrating film including one of a pair of electrodes facing each other across a gap serving as a cavity, is supported so as to be capable of vibrating. A configuration unit which includes one or more cells and is electrically independent is called an element. Acoustic waves (typically ultrasound) are transmitted and received in increments of such elements.
Specifically, upon acoustic waves (typically ultrasound) being received in a state where there is potential difference between the two electrics, the vibrating film vibrates, which changes the distance between the two electrodes, thus causing change in the electrostatic capacitance. Current generated by electrostatic induction is output from each element to a reception circuit. The reception circuit converts current values into voltage values, and outputs as received signals.
Also, upon transmission signals of AC voltage being applied across the two electrodes in each element, from a transmission circuit, the vibration film vibrates, whereby acoustic waves can be transmitted from each element.
In an arrangement where multiple elements are disposed so as to form an element array, wiring for electrical connection to transmission/reception circuits is laid for each element. A flexible printed circuit is often used for the wiring, each electrode being connected to the wiring of the flexible printed circuit by way of electrode pads at an end face of the element substrate where the elements are provided. Using a flexible printed circuit enables multiple lines to be extracted in a flexible manner.